Overview
CEN ISO/TR 12489:2016 (ISO/TR 12489:2013) is a technical report that provides guidance for reliability modelling and probabilistic calculation of safety systems in the petroleum, petrochemical and natural gas industries. Endorsed by CEN and prepared by ISO/TC 67, it aims to bridge the gap between state-of-the-art methods and practical application of probabilistic techniques for safety system assessment. The report focuses on random failures and probabilistic methods; deterministic elementary hazard analyses (PHA, HAZID, HAZOP, FMECA) are out of scope but recognized as essential inputs.
Key topics and technical requirements
- Modelling approaches: analytical formulae (low-demand mode), Boolean methods (Reliability Block Diagrams, Fault Trees, Event Trees), Markov models, Petri nets, and Monte Carlo simulation.
- Operational modes: guidance for safety systems in on-demand (reactive) and continuous (preventive) modes.
- Failure classification and safe-failure concepts: definitions and taxonomy for random failures; treatment of dependent and common‑cause failures.
- Human factors and maintenance: consideration of human actions, testing, repair, and maintenance strategies in probabilistic models.
- Reliability data: sources, required data elements, field data collection and handling of numerical uncertainty in reliability parameters.
- Documentation and assumptions: requirements for recording modelling assumptions, limitations and the chosen analytical approach.
- Typical applications: worked examples for single-channel, dual-channel, redundant architectures, multiple safety systems and emergency depressurization systems.
Practical applications and users
This technical report is intended for:
- Reliability and safety analysts performing probabilistic risk assessments (PRA) and safety integrity evaluations (SIL studies).
- Designers and engineering teams in oil & gas facilities implementing safety instrumented systems (SIS), emergency shutdown and depressurization systems.
- Asset owners, operators and regulators who need transparent, documented probabilistic assessments of safety systems.
- Consultants and software tool developers building or validating modelling tools (RBD/FTA/Markov/Petri net/Monte Carlo).
Use cases include quantifying safety function reliability, comparing architecture options, modelling dependent failures, and estimating risk contributions from safety systems.
Related standards and notes
- ISO/TR 12489 complements elementary hazard analyses (PHA, HAZOP, HAZID, FMECA) by using their outputs as inputs to probabilistic models.
- It sits alongside other ISO and industry guidance on safety instrumented systems and risk assessment; users should align modelling outcomes with regulatory and company-specific safety requirements.
Keywords: ISO/TR 12489, reliability modelling, safety systems, petroleum industry, natural gas, probabilistic calculation, fault tree, Markov, Petri net, Monte Carlo, common cause failures.